High-voltage circuit breaker



Jan. 13, 1953 J. D. woon 2,625,628

HIGH-VOLTAGE CIRCUIT BREAKE R Original Filed Jan. 1l, 1947 3 Sheets-Sheet l l o 26e 6 mr v 6 26B/e e) 0 I 'a Il i) Impr-"ww a.

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Jan. 13, 1953 J. D. woon HIGH-VOLTAGE CIRCUIT BRAKER 3 Sheets-Sheet 2 Original Filed Jan. ll, 1947 o do Jan. 13, 1953 J. D. woOD 2,625,628

HIGH-VOLTAGE CIRCUIT BREAKER Original Filed Jan. 1l. 1947 3 Sheets-Sheet 3 IN VEN TOR,

BY Joseph D. Wood Attorneys Patented Jan. 13, 1953 HIGH-VOLTAGE CIRCUIT BREAKER Joseph D. Wood, Upper Darby, Pa., assignor to I T E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Original application January 11, 1947, Serial No. 721,648. Divided and this application June 28, 1947, Serial No. 757,739

(Cl. 20G-147) 2 Claims.

My present invention, which is a division of U. S. application Serial No. 721,648, led January 1l, 1947, relates to high voltage high capacity circuit breakers, and more particularly to circuit breakers having an interrupting rating of 50,000 kva. and better in any Voltage range between 2300 and 5000 volts and at current ratings of 600 and 1200 amperes.

In high capacity circuit breakers which are designed to interrupt arcs of substantial kva.,

it frequently occurs that the blow-out mechanism will eiectively move the arc into the arc chute causing it to be extinguished at or near the full rated interrupting capacity, while the blow-out mechanism is not able to perform the job of moving the arc up into the arc chute at very low current values represented by the charging currents of transformers or cables owing to the fact that the iiux through the blow-out mechanism or coils is very low and ineffective. This has resulted, in some prior art circuit breaker construction, in the addition of further devices such as puiiers and the like to assist the blow-out coil in performing its operation. A1- ternatively the prior art blow-out coil has been provided with suiiicient turns to obtain the required ampere turns even for low current failures. Such prior art devices have thus utilized the expedient simply of assisting an ineffective construction by adding additional construction thereto rendering is unnecessarily bulky.

A primary object of my invention is the arrangement and construction of the blow-out mechanism oi my novel circuit breaker so that it may move an arc at low interrupting current breakers, an important problem always present if is the transfer of the arc rom the main contacts to the arcing contacts. An object oi' the present invention resides in a novel construction of main and arcing contacts and oi an auxiliary contact with relation to the movable contact arm for a rapid transfer of the arc to the auxiliary contact and movable contact.

In accordance with the present invention a novel circuit arrangement is provided for the blow-out coil whereby the arc formed on opening oi the contacts is in parallel with the blow-out coil and provides a by-pass circuit around the blow-out coil of a predetermined impedance in relation to the impedance of the blow-out coil.

Accordingly a further object of the present invention is the provision of novel by-pass arcing circuits in relation to the blow-out coil.

The foregoing and many other objects of my invention will become apparent from the following description of the drawings in which Figure l is a side view in perspective, partly broken away showing my novel circuit breaker assembled and mounted on a truck.

Figure 2 is an enlarged side front View in perspective partially broken away showing the lower terminal assembly, upper terminal assembly, the blow-cut coil assembly and the movable contact bridge assembly.

Figure 3 is a detail of the construction of the front end of the lower terminal of my novel circuit breaker.

Figures 4 and 5 are schematic views of the arcing contacts and blow-out coil of my novel circuit breaker,

Referring now to Figures 1 and 2, my novel circuit breaker is shown preferably mounted on a movable truck. The movable truck comprises a back main supporting structure which includes the vertical support members I 0 and I l connected together and interbraced at the lower end by the Masonite panel l2 and at the central and upper portion by the cross-bars 13, i4 and i5 which are connected as shown, in any appropriate manner, as for instance by bolts and nuts to the vertical members 40 and il. The lower ends of the vertical members l0 and ll are provided with bearings l'l and i8 for the shaft I9 which carries the rear wheels 20 and 2l of the truck. The vertical members I0 and Il together with the cross bracing elements above described and the wheels 20 and 2l constitute a single unitary member of assembly,

Certain of the assemblies are standard and require no specific discussion here. Thus, the control panel assembly 4? and the trip unit assembly 48 may be substantially standard units which require no specic description. Also, the control switch contacts indicated generally at 10 of Figure 1 and the grounding contacts ll, 12 of Figure 1 may be standard units. The essential elements n as above pointed out with respect to these units is the unit assembly arrangement which is possible with the construction herein shown.

The rear end of the operating mechanism assembly iS is supported on the cross bai` 'hl which is held bythe bolts 15, 'l5 across the top of the lower panel I2. Cross .bar lil also provides means for supporting additional assemblies. The specie novel assemblies or sub-assemblies shown in Figure 1 and forming an essential part of the novel circuit breaker here shown are the lower terminal assembly shown in Fig-ure 2, the upper terminal assembly of Figure f2, Yand the movable contact arm or bridge assembly of Figure 2. The specific operation of these individual assemblies renders possible the entire high speed high capacity circuit breaker which my novel unit embodies.

The various assemblies above mentioned will be described in order, going from the bottom toward the top .of the `circuit breaker without specie emphasis on Yany one of the assemblies over the other.

It must be emphasized, however, that an important feature of the circuit breaker is in the novel `arc chute vconstruction in conjunction with the novel blow out construction.

The operating mechanism utilizes as closely as possible thesimple principle vof the lever operated switch Vwith only enough addition thereto to provide automatic response to over-current conditions in order to trip the circuit breaker and also to provide a solenoid closing means. The simplincationof this operating mechanism makes possible the production -of the inexpensive circuit breaker herein described.

Thus, while the arc chute assembly and the blow-out assembly make possible the high capacity operation and high speed operation which are essential to the operation of the circuit breaker as a whole, the simplicity of the other assemblies makes possible the economical Yand efcient construction.

The individual -unit assemblies facilitate :storage of parts preparatory to nal assembly and v thus makes it possible to ll orders yquick-ly.

Thus the first sub-assembly which consists of the back panel and the back wheels 20 .and 2l is essentially a, simple flat member which may readily be Astored and does not take up :any 'substantial amount -of space (see Figure l).

Heretofore, the dirhculty encountered in premanufacture of sub-assemblies in anticipation of future orders resided in the fact that the main frame of the circuit breaker or other switch gear usually was as big as the circuit breaker itself, so that the manufacture and especially the storage of the main frame presented the same problem as the storing of an entire circuit breaker. No real economy was effected by pre-manufacture 'of the main frame since the entire y.circuit breaker could be stored just as readily.

By means of my novel device, the back panel and the rear wheels of the truck which constitute a single flat structuremay readily be stored 'awaiting specic orders for .assembly or specific circuit breakers.

The truck structure `is completed by means of a lower or bottom platform which carries a front wheel 2G in the front swivel 25 (Figure 1).

The bottom platform 23 is secured at the rear end to the lower end of the vertical members In and II above the bearings Il and I 8 for the rear wheel. The bottom platform 23 in connection with the back panel form the vertical supporting members lil and Il and their interbracing structure and taken together with the rear wheels 20 and 2l and the front swivel wheel 24 comprises the truck or mounting for the circuit breaker. Thus the bottom platform 23 and the front swivel wheel .24 constitute a fsi-ngle sub-assembly which may readily be stored withoutrequiring any additional space and which may readily be attached by two screws to the lower end of the vertical members I0 and I I.

This type of unitary sub-assembly construction Ywhich may .readily be interconnected with other elements in order to make a complete truck, facilitates modication and of Variation of subassemblies in order to meet the speoic orders.

Thus in Vthe :event various control elements must lbe multiplied to a substantial extent in the 'final circuit breaker thus requiring perhaps a custom built lower platform 23, this lower platform 23 may be built to the unique specifications of -the customer and may then be combined with the standard back panel construction which is kept in stock. However, the entire truck construction including the first-and second sub-assemblies above described are built in full anticipation of lall requirements to which the particular circuit breaker may Abe put, so -that .particular 'custom made back or bottom portions of a truck will be required -only in exceptional cases. The upper terminal assembly 30, and the lower terminal assembly 3I for each of the three poles is formed from a single bar of copper of rectangularcross section appropriately insulated :by .phenolic insulation as described more specically hereinafter in connection with Figure 2. The terminal assembly elements SEE, 3l are lcarried by the vertical supports Island I I,.as well as .the-central Vertical support 32 which is carried between the lower Masonite plate I2, and the upper cross bar I6, as 4shown in Figure V2.

Each of the vertical members I0., .Il and 32 is recessed at 3.3, 33 to .receive the terminal members and accurately position .the same.

Each .of the upper and lower terminal assembly members 39 and SI also carry the spring biased disconnect contact elements 38, 38 also hereinafter more specifically described in connection with Figure l, but shown also in Patent Number 2,029,028. The intermediate cross bar I3, which is secured to the vertical members l, i I and 32 by v.the bolts 40, also carries at its outer end the wheels #i2 on an .appropriate shaft extension thereof, the said wheels 42 cooperating with appropriate tracks .in the compartment to guide the truck into and out of the compartment properly.

The racking and indicator assembly shown generally at i3 of Figure l also carries the front kwheels 4, 44 t0 ride on the guide tracks of the compartment in which the circuit breaker is housed.

The racking and indicator assembly d3 is supported from the mechanism assembly. The control panel assembly Il is supported by the lower platform 23 of the circuit breaker as is also the trip unitfassembly 8. The solenoid closing mechanism lle is a part `of the operating mechanism assembly 5.

The movable contact assembly shown generally at 50 ofFigures V1 and 2 is connected at its lower end to the lower terminal assembly Si in the manner hereinafter described, and is provided with a link 5I which is connected to the Contact operating `arms 52 projecting up from the operating mechanism assembly d. The movable contact :bridge assembly which of course has as vmany poles as there are upper and lower terminal assemblies, three in the particular instance shown, is provided with contact elements hereinafter more particularly described in connection with Figure 2. The blow out coil assembly 53 which includes the coil 54 of Figure 2 and the laminated blow out iron legs 55, is mounted on the upper insulating back panel 55 also across the bars I5 and I4 and the upper portion of Vertical supporting members l and and is supported thereby.

It is spaced from the bars I5, |I, 32, i4, I by the upper insulating back panel 55 which panel is secured across the bars I0, and 32 as shown in Figure 2. Appropriate openings 59, 59 are provided in the panel 56 to permit the terminal members 3|! and 3| to project therethrough in a manner shown in Figures 1 and 2.

The arc chute assembly 5? is supported by the blow out assembly 53 and particularly by the laminated legs 55 of the blow out iron which ride between the bracing bars 58, 58 on each side of the arc chute as shown in Figure l and as will be more specifically described hereinafter in connection with Figures 1 and 2,

Lower terminal assembly The lower terminal assembly 3| shown in Figures 1 and 2, comprises a oar of copper I5!) insulated by an oblong Bakelite tube I5! with a conductive inner lining into which it has been pressed. The front end |52 supports the movable contact bridge assembly 50 in a manner hereinafter specically described, while the main disconnect contacts 38 are secured to the rear end The lower vterminal 3| has the side flanges |55, |56 secured thereto in any suitable manner, to cooperate with the movable contact arm as shown in Figure 2. In the usual procedure for insulating a terminal bar such as that shown in Figures 1 and 2 phenolic insulation material is wrapped around the bar and tightly pressed thereon. This is a complicated process which must be performed on sp-ecial machinery and by f those having special skills in the eld.

In the present construction, instead of wrapping phenolic insulation tightly around the bar |5U, the nat tube |5i is used, said tube being provided with a conductive lining |62. rThis tube is placed over the bar |59 and then pressed into tight engagement with the bar |511 to provide the insulation cover therefor.

The principal reason for wrapping the insula- .tion in the prior art was that no minute air pockets could be permitted since at high voltages these would result in corona discharge, causing progressive dielectric deterioration and thereby resulting in breakdown of the insulation. Consequently great care was required in the wrapping of the insulation.

I have discovered that by using a sleeve of insulating material and making the inner surface of the sleeve conductive, the sleeve may simply be pressed down around the tube to conform with the contour of the bar and provide a completely engaging surface to surface contact thus according any deleterious eiects resulting from any minute air pockets that may remain. Thus where the prior cost of wrapping such bars was in the neighborhood of $12.0() per bar and it was necessary to send. the bar out to be wrapped by special machinery, my invention makes possible the insulation 4cf the bar at the circuit breaker plant at a cost of about $1.50.

Upper terminal assembly The upper terminal assembly shown in Figures 1 and 2 also comprises a bar |50 of copper having an insulating sleeve IEiI mounted thereover in the same manner as previously described in connection with the lower terminal assembly Figure 2.

The rear end of the bar ISD has the conformation |513 to receive and hold the main disconnect contacts 38 shown in Figure 1. The front end of bar IEB has secured thereto the stationary main contact 161 and the stationary arcing contact |66 (Figure 2). The upper end of the front portion of bar has secured thereto the insulating blocks |85 and |68 (Figures 1 and 2), which have secured thereto the insulating plate |10 having the upper slotted extension Illia. Connector is secured in any suitable manner to the insulating blocks and |58 but is insulated from the contact bar |69 and the arcing contact |66 and stationary contact |67.

Connector l'iI has a cut away portion at its front end between which, and spaced from either edge, 'the forward end 203 of the movable contact arm 294 comes to rest when the contacts are in engagement as will be described hereafter.

M ooclble Contact assembly In Figure 2, I have shown one of the contact arms 80. The contact arm 20 comprises a pair of copper bars |86, It! between which is secured, at the upper end by pin 255, the arcing contact arm 204. The movable arcing contact-arm 234 is held in proper spaced relation by the spacer washers ISG-|34, all of which are forced into proper current carrying relation by the spring washers 233-235. The upper inside edge of the copper bars Ii--iiil carry special arc resisting silver alloy contact blocks 85 which comprise the main movable contacts.

The lower ends of the bars Ito and ISI are provided with the registering openings to receive the pin |81 (Figures 1 and 2) which pin passes through the openings and. through the slotted openings |33 (Figure 3) of the front end |52 of the lower terminal SI which is received between the arms |8e-|8|- The pin |51 is provided on each side with a lug |50 (Figures 1, 2 and 3) carrying the bar |9| which passes through openings Ila (Figures 2 and 3) of the side flanges |55. Compression springs |93 on each side are captured between ilanges |55 on each side and the lug |92 of pin |81 on each side thus forcing the lower end or pivot of the contact arm out toward the right with respect to Figures 1 and 3 at the pivot point |36.

IThe contact arm effectively pivots about pin 2&8 (Figures l and 2) which is connected between the arms lai and |89 and which carries the end of link 5| connected to contact operating arm 52. Thus, compression springs |93 force the contact arm Si] to rotate counterclockwise about the pin 255 within the limit of the length of slot |88 on the lower terminal and thus forces the movable contact |55 into close wiping engagement with the stationary contact member IE? (Figures 1 and 2) In any position of the arm other than the closed position of the arm Sd, compression springs |93 push the pin |55 over to the iar right end slot |83 of the lower terminal of Figure 2. When the contact arm reaches the closed position of the contacts, the movable contact |85 bears against the stationary contact |51 and as the link 7 forces pin 26B and contact arm 8B into the closed position, the spring |93 yields because of the slope of the angular slot iBilto permit the wiping action to occur between the contacts |25 and it? and the contacts to close firmly.

The forward end |52 of the lower terminal of Figure 2 is provided with silver alloy inserts 222, 262 to bear against the inner surfaces of arms |80, |8| of contact arm 3Q. Thus it will be seen that no pigtails are used, but appropriate elements are used on pin it? to squeeze the lower ends of arms |8I, itil against the insert contacts 22 on the lower terminal.

The contact springs la are located close to the pivcted stud i-S'l which is a distinct advantage because they are well away from the arcing zone. The connection of link ci to the contact arms is at a point 22e, as above pointed out, well above the center point of the arms 32, so as to make these contacts blow-on contacts as explained in the following description.

In response to a rise in currents, magnetic forces developed in these contacts tends to increase contact pressure at all Contact points. The

arcing contact arm 221i is pivotally mounted on f the pin between the contact arms |88, |8| and the spacer' washers ist, and is provided with an arcing contact element 2st and the horn 2li?. The lower end of arcing contact arm 2M is connested by the floating pin 2MB to the link 2|! which in turn at this lower end bears against the milled surface 252 oi the milled pin 2|3 carried between the springs I8 i.

Tension spring 2id connected between lug 2|S and spring eye 2i? is arranged to rotate link 2| clockwise around the bearing furnished by the milled portion 252 of pin 2 i3. The lug 255 is adjustably mounted on screw 225i which-in turn is received in the 'tapped opening 22| of pin 222 carried between the arms E85, |81, Rotation of screw 22@ results in moving lug Zit to change the tension of spring Zie and thus increase the bias thereof.

Spring 2&5 thus acts on links 2li to cause the toggle 2i|2it`-2d2 to collapse in a direction to force the arcing contact 295 to the left. The full collapse of this toggle is prevented by the adjustment of screw 22! which bears against the end 225 oi arcing contact arm 22d. Tension spring 2i5, however, thus drives the arcing contact element 29S out to the left with respect to Figure 2 where it will make contact with the stationary arcing contact |56 before the main contacts engage and where it will maintain contact with the stationary arcing contact until after the main contacts have separated.

Since the center 225 of arcing contact arm 2E!! is well above the mid-point thereof, a blow-on action of the arcing contact occurs, also thus ensuring that the arcing contacts will remain firmly in engagement until the main contacts have separated.

The position of the arcing tips 205 above the main contacts ii'! forms an upward loop in the circuit which tends to initiate a blow out action to start the arm upward when drawn.

In order to protect the lower terminal structure against any possible defect in the arc chute or blow-out `mechanism which would tend to drive an arc down, an insulating shield ESQ is provided secured to the screws |82 and ared out to protect the uninsulated portion of the lower terminal bar |50.

Spring 2 i ensures that the movable arcing contact will move into engagement with the station- 8 ary 'arcing contact as the vcontact arm begins to open 'and before the main Contact separates. The arcing contacts will then stay in engagement for a substantial portion of the opening movement 5 depending on the setting of screw 229 (Figure '2).

Elow out assembly The blow-out assembly 53 comprising the coil ed and the laminated blow-out iron legs 55 already referred to in Figure l, is shown more specically in Figure 2. The coil "1li is connected by the lead 235 and bolt 23d (Figures 1 and 2) to the upper terminal bar The opposite end or" coil 5a is connected by lead 23e to extension lila on contact bar il'i passing through a slot in the upper extension Htc; ci insulating strip i'i (Figure 2). Coil 5d is wound on an iron core 22S to which is secured the laminated blow-out iron legs 55 on either side.

I have found that preferably four such side plates en each side 1/8 thick ensures a proper distribution of magnetic blow-out iiux over the iull length of the side plates. Also I have found that in order to obtain a proper blow-out flux without inserting too much impedance in series with the arc it is desirable that the coil 56% consist Vci i8 turns of copper strips of 136 X lThe side frame members 2512, 222 (Figure 2) sembly are secured against the by bolts which also secure the plates against the The side frame members 2f? of the blow-out assembly have secured therebetween the upper block by means of pin 2626 and the lower block (not shown) by means of pin and plate by means of screws 252.

Block and its corresponding lower block are provided with tapped openings by means of which the entire blow-out assembly be readily secured to the frame ot the circuit breaker. lt will thus be seen that the entire blow-out assembly may be readily mounted on and removed from the circuit breaker' as a single unit.

Arc chute The blow-out assembly serves as support for the arc chute described in Figure 2. The are chute assembly 5'? mounted above the contact assembly SS provides for a positive and efficient arc interruption. lt consists oi insulation side walls 257, front and back arc runners 722i and 2Q@ respectively (ligure i) and series of ceramic plates moun ed in spaced relation transverse of the arc path and a strong magnetic blow-out eid to force the arc into the arc chute.

The sides 2d? have fastened at their lower portion, adjacent the arcing area, inner arc resisting insulating plates 2%9--2552 of special composition hereinater described. The arc resisting plates 2F39 are chamfered along their upper edges at 222-252 to provide straight locking edge for the cross plates 25d and the spacers 26|. The lower ends of the cross plates 25s and the spacers Zei are appropriately shaped to iit the chamiered edge 262.

As the arc is driven into the chute by the magnetic field, it passes rapidly through the arc extinguishing ceramic plates 2te which are rectangular in shape at the top and have a long tapered lower edge extending from the center of one side of the plate to the lower corner on the opposite of the plate. A ceramic spacer 25| is provided to support each plate and position it with respect to adjacent plates and forms with the long tapered surface of the plate, a triangular opening with the Vapex at the top of the passage of the arc. Each plate with its spacer presents a decreasing area for the arc as it rises and gradually squeezes it into a narrow slot 301.

The plates 269 are assembled alternately in an interleaved relation and spaced from each other so that the long tapered surfaces cross at the center of the chute directly above the path of the arc as it travels up the chute. As the arc passes the crossover' point of the plates it is forced into a zig zag or sinuous path gradually but rapidly increasing its length and bringing it into contact with larger and larger cool surfaces of the plates. rlhe arc must thus bend around the edges of the plates which are effective in circuit interruption. The positive and eicient arc interruption is aected by the cooling, lengthening and squeezing of the arc at numerous points all along its path.

Provision for the interruption of low current arcs is built into the ar-c chute. No moving parts or auxiliary equipment are necessary. Short circuit or normal overcurrents are extinguished before the moving arc horn 291 passes the front arc runner 29|. The arc formed by currents of low value is extended in the chute beyond the front are runner 29! and effectively cooled and deionized by a set of plates 322 located in the current path.

The side plates 251 are connected together at the front and back end of the arc chute by bolts 29B. The side plates are provided with insulating bracing bars 58 secured thereto by the bolts 268 and spaced apart by the width of the laminated blow-out iron legs 55.

The materials used in the construction of the arc chute play an extremely important part in the performance of the circuit breaker.

The side plates 251 are made of Bakelite with a layer of libre on each side. During interruption not only full voltage is applied to these plates but frequently switching surges of very high value are encountered. The high insulating value of Bakelite is desired but it alone would not be satisfactory since it has the characteristic of carboniaing and tracking if any arc or high temperature arc gases come in contact with it. Consequently, the Bakelite is coated with libre which does not have this characteristic. Furthermore, an arc-resisting insulating varnish is applied to the libre to keep it from absorbing moisture. Furthermore, the spacers 26| for the cross-plates 259 completely line the inside of the arc chute in the lower part where the arc is drawn and prevents the arc coming in contact with the side plates at any point.

The material of Which the cross plates 269 and the spacers 26| are made, determines to a large extent the ability of the breaker to interrupt currents. 'The least expensive material that is at all suitable for this application is the asbestos cement board called Transite. This material gives fair operation and for low interrupting capacities is quite suitable. 1n an eiort to increase the interrupting capacity, numerous materials were tried. Gas forming materials such as libre were found to be unsatisfactory as they increased the display incident to circuit interruptions and the excess gas had a tendency to initiate arcing in other parts of the breaker. Inert materials were better. Porcelain, while quite good was too fragile and could not be manufactured in thin plates with sufficient accuracy to make i1; practical.

By far the best material found was the glass bonded mica consisting of mica dust and glass fused and pressed at high temperature and pressure. It is inert at the temperatures encountered in the arc chute, an excellent insulator, does not absorb moisture and is a nongasforming material. This material when used for the arc plate and spacers increased the interrupting capacity to more than twice the value shown by other materials. It is used not only for the cross plates 260 and spacers 25| but also for the arc resisting plates 259 that come in contact with the arc.

The arc chute may be mounted in position by being slid on to the laminated blow-out iron legs 55 so that the reinforcing bars 58, 58 act as runners to receive the laminated legs 55 in the manner shown especially in Figure 1, thus holding the arc chute in position.

In order to ensure a further distribution of magnetic blow-out flux down into the region of the contacts, an additional iron plate 219 (Figure 1) is provided on each side of the arc chute secured to the bracing bars 58 by screws 21| and having extension 212 extending down into the region of the contacts outside the plates 51.

The blow-out flux through the laminated blowout iron legs 55 is also communicated to plate 219 and by extension 212 is communicated down into the region of the contacts to increase the blowout eflect in that region. The runners or bracing bars 58 on one side of the arc chute are provided with the bronze springs 239 connected be- `.tween the runners or bracing bars 58 by screws 28| and a latch assembly 5| secured thereto in any suitable manner as by screws 283, 283 and having a projection 282 which engages a corresponding detent 284 in the laminated iron leg 55 (Figure 1). Thus the arc chute is supported by lthe laminated legs 55 between runners 58 on each side and is latched in position by the latch assembly 5| engaging detent 234 in laminated legs 55. To remove the arc chute it is only necessary to press in the latch assembly 25| to disengage the detent 284 from laminated iron legs 55 so that the arc chute may be slid out. As already stated, the arc chute is provided with a back arc runner 299 and a front arc runner 29| converging below the arc chute and toward the center in the region of the contacts, the front arc run ner 29| having extension 29| toward the contacts and the further rearward extension 293.

The portion |1|A (Figure 2) of the upper ter minal to which lead 238 of the blow-out coil is connected is also provided with the spring clip 30D (Figures l and 2) to receive the rearward extension 293 of the rear arc horn 29B of the arc chute 51. Thus no special connection need be made for the arc chute; but when the arc chute is slid into position, the rear extension 293 of the rear arc horn 299 moves into the spring clip 399 and the rear arc horn is thus connected to the end 238 of blow-out coil 54.

The section 299B of the rear arc horn rests on plate |1| to obtain further contact to the rear arc horn 299. Thus when the section of the arc on the stationary arcing contact jumps to section 290A of the rear arc horn, the current path is from terminal 38, bolt 236 to lead 235 to coil 54 to lead 238 to section |1|A of member |1| and spring clip 39d. Then from spring clip 399 to section 2995 of rear arc horn 299. Then through the arc chute to the movable arcing contact and then to the front arc runner 29| as hereinafter more specically described.

The cross plates 269 are each of an insulating non-carbonizing material, preferably a glass bonded, mica ceramic material or of a material known as Transite. These plates are longitudiacaaeae nal members having a curve at section 3GB of a very large radius; upward of this position they have a curve 3M of smaller radius; and above that position have an extension 305 entering the notch 25B and closing ofi that side of the plate.

The side of each plate opposite the curve is flat. When the arc is lirst drawn it is driven up by the blow-out mechanism into the notch t i t of V-shaped cross-section formed by the curves @G3-Stili of the alternately arranged plates. As the arc is driven up further beyond the apex of the notch, it is caused to Zig-zag laterally in flowing past the curves Stai of the alternately arranged plates. It thus passes through the relatively narrow notch Sill on one side of one plate and then through a similar relatively very narrow notch on the opposite side of the alternate plate and back and forth laterally through the arc chute.

If the arc is not extinguished when the arc has reached this point, the magnetic blow-out blows the arc up still further past extension 3ds where in addition to the lateral zig-zagging and lengthening of the arc, the arc is Zig-zagged vertically. This combination of extreme lateral zig-Zagging with vertical zig-zagging of the arc ensures extinguishment of the arc before the top of the arc chute is reached. rl'he combination of lateral zigzagging with vertical zig-.zagging limits the upward travel of the arc.

Thus it will be seen that one of the essential elements cf the arc chute herein described is rst the lateral zig-zagging or lengthening of the arc as it is blown up into alternatingr thin narrow slots on each side. Thereafter the portion of the arc between the cross-plates 2% is free to move up to superimpose on the lateral zig-zagging or lengthening of the arc, a vertical zig-zagging or lengthening.

Also it will be seen that there is no connection whatever between the front arc horn 29! and the lower terminal or any other terminal when the circuit breaker is closed or open.

The eilect on the arc between lll-B and 2&8 which is horizontal is to drive it rapidly up the runners 290 and into the arc chute 5l. The effect on the arc between I' l-B and |66, which is vertical, is to drive it back against the insulating and heat resisting block |68. This insulating block may be provided with slots, grooves, holes 583 (Figure 5.). or other cooling means to deionize the arc and eiect the blow-out characteristics of the breaker. It will beV apparent that the size, shape and spacing of the extensions N2 will also effect the blow-out characteristics.

It will also be noted that the conductive bar lll has a U notch indicated generally at llB therein, in which the portion 2% of the upper arcing horn 207 registers, thus provided for sirnpliied transference of the arc to the contact bar ill and` hence to section 2Std of the rear arc runner 296 of the arc chute 57.

The insulating shield 239 above described in connection with Figure 3 prevents a low current arc from being blown down accidentally contacting the terminal 3l. Oscillograph tests have shown the rates of arc extinguishment ranging from .58 cycle at 63,200 kva. (4200 volts) to 2.5 cycles at 3728 kva. (5000 volts).

The arcing time may be even slower at lower voltage and current values, but these values illustrate the efciency of my novel device.

In the foregoing I have described my invention solely in connection with illustrative embodiments thereof. Since many variations and modiiica'- l2. tions of my invention will now be obvious to thosek skilled in the art, I prefer to be bound not by the specic disclosures herein contained, but only by the appended claims.

I claim:

1. In a circuit breaker for protecting an electrical system, a rst contact, a blow-out coil having one terminal connected to said iirst contact, a conductor having a U-shaped notch, an insulation block between said rst contact and con-A ductor for spacing said contact from said conductor, the second terminal or" said coil being connected to said conductor, a movable contact for cooperating with said first contact, an arcing horn on said movable Contact, the forward portion of said arcing horn extending into said U-shaped notch and spaced a predetermined distance from said conductor when said movable contact engages said iirst contact, said conductor being positioned above said rst contact, a magnetic cir. cuit energized by current flowing in said blowout coil, said magnetic circuit including magnetic material extending from above said conductor downwardly toward said conductor so that on separation of the movable contact from said fixed contact in response to a fault current in said si stem being protected by said circuit breaker, the distance from said conductor to said arcing horn does not change substantially during the first movement of said movable Contact and the arc formed between said iixed and movable contact is driven upwardly against said insulation block and to said conductor when said fixed and movable contact separation has reached a distance at which the impedance of the gap from said fixed contact to said conductor and from said conductor to the forward portion of said arc horn is less than the impedance from said xed to said separated movable Contact, the voltage drop across the gap from the xed contact to said conductor produced by the are thereacross appearing across said coil. v

2. In a circuit breaker for protecting an electrical system, a first contact, a blow-out coil having one terminal connected to said rst contact, a conductor having a U-shaped notch, an .insulation block having slots at its open end, said block extending between said conductor and irst contact for spacing said Contact from said conductor, the second terminal of said coil being connected to said conductor, a movable contact for cooperating with said rst contact, an arcing horn on said movable Contact, the forward portion of said arcing horn extending into lsaid U-shaped notch and spaced a predetermined distance from said conductor when said movable contact cngages said first contact, said conductor being positioned above said rst contact, a magnetic circuit energized by current flowing in said blowout coil, said magnetic circuit including mag-A netic material extending from above said conductor downwardly toward said conductor so that on separation of the movable Contact from said fixed contact in response to a fault current in said system being protected by said circuit breaker, the distance from said conductor to said arcing horn does not change substantially during the rst movement of said movable contact and the arc formed between said xed and movable contact is driven upwardly against said insulation block and to said conductor when said iixed and movable contact separation has reached a distance at which the impedance of the gap from said iixed Contact to said conductor and from said conductor to the forward portion of said 13 arc horn is less than the impedance from said ixed to said separated movable Contact, the voltage drop across the gap from the fixed Contact to said conductor produced by the arc thereacross appearing across said coil, said magnetic circuit including iron for said blow-out coil extending on both sides of the path of movement of said movable contact, substantially parallel thereto.

JOSEPH D. WOOD.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number 14 UNITED STATES PATENTS Name Date Steinmayer Jan. 17, 1928 Baker et al. Aug. 16, 1932 Ellis et al. Nov. 12, 1935 Tamsitt Nov. 17, 1936 Crabbs July 16, 1940 Seaman Dec. 31, 1940 Thumim July 20, 1943 FOREIGN PATENTS Country Date France Nov. 3, 1938 

